SGER: Independent Determinations of Bromine (Br) and Chlorine (Cl) in Barrow, Alaska

该项目利用计划于2005年3月至4月在阿拉斯加巴罗举行的北极日出实验，评估一种以前未曾测试过的量化北极对流层中卤素原子活动的方法。溴和氯等卤素自由基在近地表极地大气和遥远的海洋边界层中催化臭氧破坏光化学循环，从而在一定程度上控制全球选定区域对流层下部的氧化能力。目前北极春季边界层的化学输送模型计算了原子溴与氯、[溴]/[氯]的比率，这与碳氢化合物损失率的观测结果不一致。PI将使用(I)通过反应从活性碳氢化合物的相对损失率推断比率的传统方法，以及(Ii)通过直接测量卤化有机化合物产品来测量以前未经测试的方法来测量[Br]/[Cl]比率。这项研究的更广泛的影响包括为一种新的方法提供一个基本的试验台，以解决模拟的[Br1]/[Cl2]比率与从现场测量推断的比率之间的混淆差异。通过更深入地了解春季极地卤素光化学和催化臭氧破坏，对这些数据的更好限制应有助于理解。这项研究还具有政策含义，因为汞循环影响到常住人口的暴露，与这些光化学循环密切相关。该项目将促进国际和平研究所以及普渡大学和阿贡国家实验室的研究人员参与的原创跨学科协作研究。该项目还将支持一名女研究生的论文研究和专业发展。该项目将由大气化学计划和北极自然科学计划联合资助的探索性研究小额赠款提供支持。

This project makes use of an Arctic sunrise experiment scheduled for March-April 2005 at Barrow, Alaska to evaluate a previously untested method for quantifying halogen atom activity in the Arctic troposphere. Halogen radicals such as bromine monoxide (BrO) and chlorine monoxide (ClO) catalyze ozone destruction photochemical cycles in the near-surface polar atmosphere and also in the remote marine boundary layer, thereby controlling to some extent the oxidizing capacity of the lower troposphere over select regions of the globe. Current chemical transport models of the Arctic springtime boundary layer calculate ratios of atomic Br to Cl, [Br]/[Cl], that are not consistent with observations of hydrocarbon loss rates. The PI will measure the [Br]/[Cl] ratios using (i) a traditional method inferring the ratio from relative loss rates of reactive hydrocarbons through reaction, and (ii) a previously untested method through direct measurement of the halogenated organic compound products. The broader impact of this research includes providing a fundamental test bed for a novel approach to addressing the confounding discrepancy between modeled [Br]/[Cl] ratios and those inferred from in situ measurements. Better constraints on these data should benefit understanding through improved insight into springtime polar halogen photochemistry and catalytic ozone destruction. This research also has policy implications in that mercury cycling, which affects exposure to the resident population, is intimately linked with these photochemical cycles. The project will facilitate original interdisciplinary collaborative research involving the PI as well as researchers at Purdue University and Argonne National Laboratory. The project will also support the dissertation research and professional development of a female graduate student. This project will be supported via a Small Grant for Exploratory Research funded jointly by the Atmospheric Chemistry Program and the Arctic Natural Science Program.